As other people have said, the other raids in FFXIV are not mandatory outside of the Crystal Tower raids. However, if you want to do the long grinds like the shiny, cool relic weapons, or have a more comprehensive grasp of the story going into Endwalker; then yes, you're going to have to do the raids. In all honesty, the raids aren't too hard and the ARR ones are the easiest out of all of them. Plus, I'd personally recommend unlocking and completing all of the raids due to getting some variety for the Alliance Roulette that can award you tombstones and gil daily.